1. Field of the Invention
The present invention relates to a head substrate having various layer films laminated on one base substrate, and an ink jet head that utilizes this head substrate. The invention also relates to an ink jet printer that utilizes this ink jet head.
2. Related Background Art
Conventionally, there have been in practice various types of image forming apparatuses, such as a laser printer, an ink jet printer. The ink jet printer is the one that forms images by discharging ink droplets. For the method of ink droplet discharges, there is an electrothermal transducing system which is called a bubble jet type.
The ink jet printer of electrothermal transducing type is arranged to keep ink liquid in the ink retaining portion comprising the nozzles, the supply paths, and the ink reservoir, and to create bubbles by heating ink liquid with the heat generating members in each of the nozzles, and then, to discharge ink droplets from the nozzles by the application of pressure exerted by bubbling of ink liquid.
Generally, for an ink jet printer, an ink jet head, which is structured to enable the ink jet printer to operate as described above, is movably supported by a carrier mechanism to travel in the main scanning direction. Then, in a position to face the ink jet head, a print sheet is sequentially carried by a sheet carrier mechanism in the sub-scanning direction.
In this way, the position where the ink jet head discharges the ink droplets and the surface of the print sheet are made relatively movable in the main scanning direction and the sub-scanning direction, respectively, hence making it possible for the ink jet head to discharge ink droplets onto the surface of the print sheet in accordance with printing data. Therefore, the ink jet head can form on the surface of the print sheet the dot matrix images by the adhesion of ink to it.
The ink jet head is structured by the combination of a head substrate and a covering member, for example. The covering member comprises the layer films that form separation walls, and a cover substrate. The head substrate is provided with one base substrate, and on the surface of this base substrate, various layer films are formed to constitute the ink discharge mechanism and others.
This ink discharge mechanism is formed by heater members for the electrothermal transducing type or formed by piezo members (elements) for the electromechanical transducing type. For a head substrate of the kind, it is generally practiced at present to provide the driver circuit that drives the ink discharge mechanism, and the data input unit through which the printing data are supplied to the driver circuit, by the formation of various layer films on the surface of the base substrate.
Further, for the ink jet head, it is proposed to install the ROM (Read Only Memory) at present on the head substrate in order to hold the data in such a manner as to read out freely the ID (identity) codes of the head itself, and the operational properties of the ink discharge mechanism. For example, in the specification of Japanese Patent Application Laid-Open No. 3-126560, it is disclosed that an EEPROM (Electrically Erasable Programmable ROM) is installed on an ink jet head.
However, the ink jet head disclosed in the above-mentioned Patent Laid-Open Application has the EEPROM which is installed separately from the head substrate. As a result, the device structure is complicated, and the productivity of the heads is not favorable. This complicated structure impedes making the apparatus lighter and smaller. Particularly, when the size of the recording data is large, the conventional ROM chip should be useful, but if the size of the recording data is small enough, it is not necessarily advantageous to provide the ROM chip from the viewpoint of manufacture costs in some cases.
Therefore, in the specifications of Japanese Patent Application Laid-Open No. 8-177732, U.S. Pat. No. 5,504,507, U.S. Pat. No. 5,536,314, or the like, it is disclosed that the ROM having the fuse array on it is formed on the base substrate of the head substrate together with the layer films of the ink discharge mechanism and others.
In this case, when the layer films of the ink discharge mechanism and others are formed on the base substrate, the fuse array that becomes ROM is formed simultaneously at the time of the head substrate manufacture.
If this fuse array is selectively fused by the control of the logic circuit which is formed together with the fuse array at a time, it becomes possible to hold the binary data by the presence and absence of fusing, for example.
Therefore, it is unnecessary to prepare the ROM chip separately from the head substrate for the ink jet heat that utilizes the aforesaid heat substrate. Then, the structure needed for holding the various readable data freely is simplified for the enhancement of the productivity. It also becomes possible to implement making the head smaller.
For the aforesaid head substrate, it is possible to hold the various readable data of the ink jet printer freely by means of the fuse array. Then, the fuse array can be formed on the base substrate together with various layer films. For the general ink jet head, the surface of the head substrate is mostly occupied by the ink retaining unit. Therefore, as shown in FIG. 9A, for example, the fuse array is formed in a position that overlaps with the ink reservoir.
In FIG. 9A, the head substrate 101 of the ink jet head 100 has the fuse member 103, the interlayer insulation film 104, the fuse electrode 105, the protection film 106, and others are appropriately laminated in a specific configuration on the base substrate 102. Then, on the surface of the protection film 106, the ink reservoir 107 is formed by the separation walls (not shown) of the covering member.
In other words, ink liquid 108 faces the fuse member 103 through the protection film 106. However, since the fuse array holds various data by means of the selective fusing of a number of fuse members 103, a considerable amount of heat is generated inevitably when the data recording is executed.
Therefore, when the fuse member 103 is fused in order to hold various date on the fuse array of the ink jet head 100 described above, the crack 190 may occur on the interlayer insulation film 104 and the protection film 106 arranged on the upper layer due to the locally generated heat as shown in FIG. 9B.
In this case, ink liquid 108 in the ink reservoir 107 is allowed to be permeated up to the position of the fuse member 103. As a result, the fuse member 103 thus fused is short circuited by the presence of the ink liquid 108 or the fuse member 103 and the fuse electrodes 105 may be eroded also by the presence of the ink liquid 108, for example.
Particularly when the fused portions of the fuse member 103 or the logic circuit for controlling the data reading drive is formed on the circumference of the fuse array, the logic circuit is also contaminated with the ink liquid 108 which has been permeated from the crack. Then, the malfunction of the fuse array or the logic circuit may take place eventually.
In order to solve a problem of the kind, it may be conceivable to laminate the protection film 106 after the data storage has been completed on the fuse array. However, if, for example, the operational properties of the ink discharge mechanism should be recorded as data on the fuse array, there is a need for fusing the fuse array after the ink jet head 100 is completed and driven.
With a view to solving the problems discussed above, the present invention is designed. It is an object of the invention to provide a head substrate which does not cause any hindrance brought about by ink liquid even when the fuse array is selectively fused. The invention is also aimed at the provision of an ink jet head that utilizes such head substrate, and an ink jet printer that utilizes such ink jet head as well.
In order to achiever these objectives, a first head substrate of the present invention for an ink jet head that discharges ink liquid retained in the ink retaining portion by the ink discharge mechanism in accordance with the printing data inputted from the outside into the data input portion comprises one base substrate having a specific position on the surface for the ink retaining portion to be arranged, and a fuse array storing various readably data freely by selective fusing. This head substrate further comprises a fuse logic circuit for controlling the operation of selective fusing of the fuse array and data reading. Then, the fuse array and the fuse logic circuit are arranged in a position in the direction orthogonal to the surface of the base substrate, but not overlapping with the ink retaining portion.
Therefore, if an ink jet head is formed by the utilization of this head substrate, it becomes possible for the ink jet head to retain ink liquid in the ink retaining portion formed on the surface of the head substrate. Then, the ink liquid can be discharged as ink droplets by use of the ink discharge mechanism formed on the head substrate. Further, the operational properties thereof and other various data can be stored on the fuse array by use of the fuse logic circuit. Thus, the stored data on the fuse array can be read out freely by use of the fuse logic circuit. Nevertheless, it is arranged that the positions of the fuse array and fuse logic circuit in the direction orthogonal to the surface of the base substrate do not overlap with the ink retaining portion. Therefore, even if a crack should occur by the fusing heat on the upper layer of the fuse array, the crack is not allowed to be permeated to the position of the ink retaining portion.
For the head substrate thus structured, it may be possible to provide the ink discharge mechanism with the heater devices (heater elements) that bubble ink liquid by the application of heat, which are formed on the aforesaid base substrate in a position below the ink retaining portion. In this case, the heater devices formed on the base substrate in the position below the ink retaining portion are arranged to bubble ink liquid by giving heat to it. Then, the ink discharge mechanism discharges ink liquid as ink droplets.
For the head substrate described above, a cavitation proof film is provided at least in a position between the heater device and the ink retaining portion for preventing the cavitation influence of ink liquid, and the cavitation proof film may be formed in the direction orthogonal to the surface of the base substrate up to a position that overlaps with the fuse array and the fuse logic circuit.
In this case, although cavitation occurs when ink liquid is caused to bubble for discharging ink droplets, the influence thus exerted is prevented by the presence of the cavitation proof film. Then, the heater devices are not damaged. Further, the cavitation proof film is formed in the direction orthogonal to the surface of the base substrate up to the position that overlaps with the fuse array and fuse logic circuit. Therefore, even if heat is locally generated by the fusing of the fuse array, the cavitation proof film prevents the influence of such heat so that there is no possibility that the crack that may take place by the fusing head of the fuse array is not allowed to be developed up to the upper layer of the cavitation proof film.
A second head substrate of the present invention for an ink jet head that discharges ink liquid retained in the ink retaining portion by the ink discharge mechanism in accordance with the printing data inputted from the outside into the data input unit (data input portion) comprises one base substrate having a specific position on the surface for the ink retaining portion to be arranged; heater devices formed on the base substrate in a position below the ink retaining portion as the ink discharge mechanism to bubble ink liquid by the application of heat; a cavitation proof film positioned at least in the gap between the heater device and the ink retaining portion for preventing the cavitation influence of ink liquid; and a fuse array storing various readably data freely by selective fusing. This head substrate further comprises a fuse logic circuit for controlling the operation of selective fusing of the fuse array and data reading. Then, the cavitation proof film is formed in the direction orthogonal to the surface of the base substrate up to a position overlapping with the fuse array and the fuse logic circuit.
Therefore, if an ink jet head is formed by the utilization of this head substrate, it becomes possible for the ink jet head to retain ink liquid in the ink retaining portion formed on the surface of the head substrate. Then, the ink liquid can be discharged as ink droplets by use of the heater devices formed on the head substrate for bubbling the ink liquid. Here, although cavitation occurs when ink liquid is caused to bubble for discharging ink droplets, the influence thus exerted is prevented by the presence of the cavitation proof film, and the heater devices are not damaged. The operational properties needed for discharging ink droplets and other various data can be stored on the fuse array by use of the fuse logic circuit. Then, the stored data on the fuse array can be read out freely from the fuse logic circuit. However, in the direction orthogonal to the surface of the base substrate, the cavitation film is formed up to the position where the fuse array and the fuse logic circuit overlap with each other. For example, therefore, even if heat is locally generated due to the fusing of the fuse array, the influence of this heat generating is prevented by the presence of the cavitation proof film. As a result, there is no possibility that the crack that may be created due to the fusing heat of the fuse array is allowed to develop up to the upper layer of the cavitation proof film. Thus, the crack does not take palace in the position of the ink retaining portion to enable ink liquid to be permeated.
A third head substrate of the present invention for an ink jet head that discharges ink liquid retained in the ink retaining portion by the ink discharge mechanism in accordance with the printing data inputted from the outside into the data input unit, comprises one base substrate having a specific position on the surface for the ink retaining portion to be arranged; heater devices formed on the base substrate in a position below the ink retaining portion as the ink discharge mechanism to bubble ink liquid by the application of heat; a cavitation proof film positioned at least in the gap between the heater device and the ink retaining portion for preventing the cavitation influence of ink liquid; and a fuse array storing various readably data freely by selective fusing. Here, the head substrate further comprises a fuse logic circuit for controlling the operation of selective fusing of the fuse array and data reading, and the ink retaining portion and the fuse array are arranged in a position in the direction orthogonal to the surface of the base substrate at least overlapping partly, and the cavitation proof film is formed up to the overlapping position of the fuse array and the fuse logic circuit.
Therefore, if an ink jet head is formed by the utilization of this head substrate, it becomes possible for the ink jet head to retain ink liquid in the ink retaining portion formed on the surface of the head substrate. Then, the ink liquid can be discharged as ink droplets by use of the heater devices formed on the head substrate for bubbling the ink liquid. Here, although cavitation occurs when ink liquid is caused to bubble for discharging ink droplets, the influence thus exerted is prevented by the presence of the cavitation proof film, and the heater devices are not damaged. The operational properties needed for discharging ink droplets and other various data can be stored on the fuse array by use of the fuse logic circuit. Then, the store d data on the fuse array can be read out freely from the fuse logic circuit. However, in the direction orthogonal to the surface of the base substrate, the cavitation film is formed up to the position where the ink retaining portion and the fuse array and the overlap with each other. For example, therefore, even if heat is locally generated due to the fusing of the fuse array, the influence of this heat generating is prevented by the presence of the cavitation proof film. As a result, there is no possibility that the crack that may be created due to the fusing heat of the fuse array is allowed to develop up to the upper layer of the cavitation proof film. Thus, the crack does not take palace in the position of the ink retaining portion to enable ink liquid to be permeated.
For the head substrate described above, it may be possible to form the fuse array with the same material of the heater device. In this case, since the heater devices and fuse array of the ink discharge mechanism are formed by the same material, there is no need for the provision of new additional material when fuse array is formed in manufacturing the head substrate.
For the head substrate described above, a barrier layer is formed on the lower layer of the heater device. Then, the fuse array may be formed with the same material as the barrier layer. In this case, since the barrier layer is formed on the lower layer of the heater device of the ink discharge mechanism, it becomes possible to prevent, with the presence of the barrier layer, the development of hillocks on the lower metallic layer due to heating of the heater device. Now that the barrier layer and the heater devices are formed by the same material, there is no need for the provision of new additional material when fuse array is formed in manufacturing the head substrate.
For the head substrate described above, a print logic circuit having various wiring lines is formed on the base substrate to control the operation of the ink discharge mechanism, and the fuse array is formed with the same material of the wiring lines of the print logic circuit.
In this case, the operation of the ink discharge mechanism is controlled by the logic circuit formed by various wiring lines and others on the base substrate. Then, the ink discharge mechanism is able to discharge ink droplets appropriately. Now that the wiring lines of the logic circuit and the fuse array are formed by the same material, there is no need for the provision of new additional material when fuse array is formed in manufacturing the head substrate.
For the head substrate described above, it may be possible to from the fuse array with the layer film on the lower layer of the heater device. In this case, the fuse array is formed by the layer film on the layer of the heater device of the ink discharge mechanism. For example, therefore, if a crack occurs on the upper layer due to the local heating due to the fusing of the fuse array, the crack thus created is not easily allowed to reach the position of the ink retaining portion.
Also, an ink jet head of the present invention comprises a head substrate manufacture in accordance with the present invention, and a covering member shielding the surface of the head substrate concavely to form the ink retaining portion. Therefore, the ink retaining portion of this ink jet head is formed by the covering member that shields the surface of the head substrate concavely. Then, ink liquid is retained in the ink retaining portion thus formed.
Also, an ink jet printer of the present invention comprises an ink jet head manufacture in accordance with the present invention; ink supply means for supplying ink liquid to the ink retaining portion of the ink jet head; data input means for inputting printing data into the data input unit of the ink jet head; relatively moving means for relatively carrying a recording medium with respect to the ink jet head; and data read means for reading out various data to the fuse logic circuit from the fuse array of the ink jet head.
Therefore, for the ink jet printer of the present invention, the ink supply means supplies ink to the ink retaining portion of the ink jet head. The data input means inputs the printing data to the data input unit of the ink jet head. the relative movement means moves the recording medium relatively with respect to the ink jet head. As a result, the ink jet head discharges ink droplets to the surface of the recording medium in accordance with the printing data. Then, the position thereof moves relatively, hence making it possible to form dot matrix images by the ink droplets that adhere to the recording medium accordingly. The data read means reads out various data from the fuse array to the fuse logic circuit of the ink jet head. For example, therefore, it becomes possible to adjust driving by recognizing the operational properties of the ink jet head from the data thus read out.
In this respect, each of the means referred to in the present invention may be formed in such a way as to implement each of the required functions. A delicately arranged hardware, a computer having appropriate function provided by programs, the functions which are implemented in the computer by the provision of an appropriate program, and the combination thereof, among some others, are regarded as those means hereof, for example.